The present invention relates to improved methods and apparatus for optically coupling pixilated scintillation arrays with position sensitive photomultipliers.
It is known to provide a miniature gamma camera using an array of position sensitive photomultiplier tubes (PSPMTs) which camera includes a scintillator layer and a light guide of one type or another as an optical coupler between the scintillator layer and the individual PSPMTs. One of the problems with such miniature gamma camera devices is the existence of so-called xe2x80x9cdead spacexe2x80x9d between adjacent individual PSPMTs in the array.
U.S. patent application Ser. No. 09/159,177 entitled xe2x80x9cMini Gamma Camera, Camera System and Method of Usexe2x80x9d filed Sep. 23, 1998 describes an improved miniature gamma camera that utilizes an array of position sensitive, high resolution photomultiplier tubes PSPMTs coupled to a scintillation layer with a light guide that effectively eliminates the xe2x80x9cdead spacexe2x80x9d between adjacent individual position sensitive photomultipliers in the array through the use of a diffusive light guide layer that, while partially successful at xe2x80x9cdead spacexe2x80x9d effect elimination is not entirely satisfactory.
Among the proposed solutions to the xe2x80x9cdead spacexe2x80x9d problem are the use of tapered fiber optic light guides between the scintillator layer and the PSPMTs that bypass the xe2x80x9cdead spacexe2x80x99 or special designs that use scintillator pixel arrays with long transversely placed scintillation pixels above the xe2x80x9cdead spacexe2x80x9d to form a bridge above and across the xe2x80x9cdead spacexe2x80x9d with scintillation light being collected at both ends. Both of these proposed solutions are very difficult to implement in a practical and manufacturable device.
It is therefore an object of the present invention to provide a method for eliminating the xe2x80x9cdead spacexe2x80x9d inherent in radiation sensitive camera and similar such devices that utilize an array of adjacent PSPMTs to receive the output of a scintillation layer via an optical coupling layer or device.
It is another object of the present invention to provide a radiation sensitive recording device that permits the elimination of the xe2x80x9cdead spacexe2x80x9d between adjacent PSPMTs that receive the output of a scintillator layer or scintillator array via an optical coupling device.
It is yet another object of the present invention to provide a simplified optical coupler that eliminates the xe2x80x9cdead spacexe2x80x9d in camera and similar devices that utilize an array of PSPMTs to receive the output of a scintillator layer or scintillator array via an optical coupling system.
According to the present invention there is provided an optical coupler for optically coupling a pixilated scintillator layer or array to an array of position sensitive photomultiplier tubes that utilizes a two-part optical coupling window comprising a first, uniform, planar spreader portion whose surface addresses the pixilated scintillator layer and optically coupled therewith a second layer comprising an array of trapezoidal light collectors individually optically coupled to the windows of an array of position sensitive photomultipliers. Incorporation of the novel optical coupler of the present invention into a miniature gamma camera is also described.